Dozens of widows of NYPD officers slain in the line of duty joined the department’s largest union Tuesday to demand that the government fix a loophole that lets paroled cop-killers back on the streets.

Career criminals out on parole gunned down the husbands of both Linda Sledge and Mary Beth Ruotolo-O’Neill. The man who murdered Cecil F. Sledge, Linda’s husband, is up for parole next month.

“Had he committed this crime today, he would have been given life without parole, which is the only appropriate sentence,” she said.

Patrolmen’s Benevolent Association President Patrick J. Lynch holds state government responsible for the change in the parole board’s decision-making policy, which could potentially free 59 cop-killers.

The longest sentence for criminals who killed cops before 2005 was 25 years to life. Those killers, who are eligible for parole after serving 25 years, are now benefiting from 2011 guidelines that look at what criminals have been doing since their incarceration, rather than just the original crime.

“Under new parole guidelines, the nature of the crime, regardless of how heinous, barbaric, sadistic or depraved, is no longer a factor,” he said during his impassioned speech at PBA headquarters.

“The guidelines have been reconfigured so if a killer admits to the crime and says they’re sorry, the jail doors slide open.”

Lynch urged Gov. Andrew Cuomo and elected officials to give the families of officers who were slain years ago the same justice that would be demanded if a cop was killed on duty today.

“The governor appointed these folks and put politics before right and wrong,” he said. “It’s no different if it happened in 1970, 1980 or any other time. The city was shocked back then and we made a promise that we would help those families get justice.

“That promise was broken. We broke it in the governor’s office. It was broken in the state Legislature. It was broken on the parole board. Shame on them.”

Cuomo spokesman told The Post in a statement that “the governor and the Legislature were responsible for reforms in 2011 that strengthened New York’s parole system, and further, the Governor proposed determinate sentencing two years ago but that effort was rejected by the Legislature.

“We of course remain open to considering any further amendments to the law that are constitutional and advance public safety,” he added.